As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE MAINTENANCE WAS PERFORMING A PRE-RELEASE AUTOFEATHER TEST, UNUSUAL VIBRATION WAS NOTED COMING FROM LT ENGINE AND PROP. ENGINE WAS SHUTDOWN WITHOUT INCIDENT AND UPON INVESTIGATION INTERNAL FAILURE WAS OBVIOUS DUE TO BLADE MOVEMENT. PROPELLER REMOVED FROM AIRCRAFT FOR TEARDOWN INVESTIGATION AND SPECIAL SOAP SAMPLE WAS TAKEN.